Process for rust-proofing iron and steel.



UNITED STATES PATENT OFFICE.

WILLIAM H. ALLEN,

OF DETROIT, MICHIGAN, ASSIGNOR 'IO CLARK W. PARKER, or

DETROIT, MICHIGAN.

rnoc'nss iron RUST-PROOFING moat AND STEEL.

No Drawing.

To all whom it may concern:

Be it known that I, WILLIAM H. ALLEN, a citizen of the United States,residing at Detroit, in the county of \Vayne and State of Michigan, haveinvented a new and useful Process for Rust-Proofing Iron and Steel, ofwhich the following is a specification.

This invention relates to the rendering rust-proof of iron and steel bychanging the surfaces of these metals to basic phosphate salts of iron.Iron when placed in a solution of such acids as hydro-chloric, sulfuricor phosphoric, is attacked and dissolved, forming ferrous salts; in thecase of the phosphoric acid, if the solution is weak, a more or lessadherent coat of insoluble ferrous phosphate is formed, which, in thepresence of an oxidizing agent becomes basic in character and black.

If a piece of iron is placed in a hot basic solution of ferric chloridor ferric sulfate, there is formed a black basic salt adherent to themetal. When the iron is removed and placed in a hot solution of analkali phosphate, such as tri-sodium phosphate or disodium phosphate,the adherent film becomes fairly permanent.

The governing of these reactions is quite difficult and impracticable. Ihave therefore invented-the following process based upon the fact thatthe more acid phosphate salts of calcium, magnesium, barium or otheralkali earth metals in solution react much less violently on iron thanwhen free phosphoric acid is present.

As the acid radical (P0 is in union with the alkali earth metal (calciumfor example), it Will not readily form soluble iron phosphate. butreadily forms the insoluble ferrous phosphate at the points of contactwhen iron is introduced. The soluble acid calcium phosphate (2CaH (PO(mono calcium phosphate) is converted into the insoluble acid calciumphosphate (Ca H,(PO,) (dicalcium phosphate). If now, during theformation of the layer of ferrous phosphate, an oxidizing agent bepresent, some ferroso-ferric phosphates are formed and the surface ofthe iron becomes black. The reaction is probably as follows:

- After removing from the solution, drying Specification of LettersPatent.

Patented Jan. 11 1916.

Application filed May 10, 1915. Serial No. 27,101.

and oiling, the iron will resist corrosion by the atmosphere.

The oxidizing agents used are hydrated manganic oxid (Mn O H O) and airwhich is passed up through the solution in any deslred manner. Theproportions of the materials employed in preparing the bath are:mono-calcium phosphate 4 ounces, hydrated mangamc oxid ounce, water q.s. to make 1 gallon. These proportions may be modified to producedifferent thicknesses and denslties of the protecting layers; Themono-calcium phosphate is also known as double super phosphate.

The solution is heated to nearly the-boiling point and the objects ofiron or steel are lntroduced. Air is forced up through the solution infine streams, contact with the objects being avoided. When the desiredcolor is obtained, the objects are removed, dried 7.5

and oiled.

The hydrated manganic oxid may be prepared from either the commercialsulfate or chlorid of manganese, by dissolving it in water with analkali such as caustic soda or slaked lime added to produce a faintalkalinity. The precipitated manganous hydrate, Mn (OH) is separated andwashed by decanta-tion, and into the mud air is blown and the manganonshydrate is thereby rapidlyil converted into the hydrated manganic 0x1 Itwill be noted that. practically no free 1. The process of rendering thesurfaces of iron or steel rust-proof which consists in immersing thesame in a solution of an acid phosphate salt of the alkali earth metalsin the presence of hydrated manganic oxid until a layer of suitablethickness of ferroso- 10 ferric phosphate is formed.

2. The process of rendering the surfaces of iron or steel rust-proofwhich consists in immersing the same in a solution of an acid phosphatesalt of the alkali earth metals in As the acid radi- 95 the presence, ofhydrated manganic oxirl until a layer of suitable thickness offerrosoferric phosphate is formed, a current of air being passed. upthrough the solution.

3. The process of rendering'the surfaces of -iron or steel rust-proofwhich consists in immersing the same in a solution of mono calciumphosphate in the presence of hydrated manganic oxid in water.

4. The process of rendering the surfaces, of iron or steelrust-proofwhich consists inimmersingthe Same in a solution of monocalciumphosphate in the presence of hydrated mangani'c oxid in water while finestreams of air are'being passed through the solution. Y

me /see immersing the same in a solution of monocalcium phosphate in thepresence of hy:

, rated manganic oxicl in water practically' --"l;- 'fiee of freephosphoric acicl; A

6. The process of rendering the surfaces of iron or steel rust-proofwhich consists in immerslng the same m a solutlon of an acid phosphatesalt of an alkaline earth metal in the presence of a manganic oxid untila layer of non-rusting material of suitable thickness is formed.

In; testimony whereof I have signed this specification.

WILLIAM H. ALLEN.

